Exercise: Phone book in JSON

Write a script that acts as a phonebook. As "database" use a file in JSON format.

$ python phone.py Foo 123
Foo added

$ python phone.py Bar
Bar is not in the phonebook

$ python phone.py Bar 456
Bar added

$ python phone.py Bar
456

$ python phone.py Foo
123

• If the user provides Bar 123 save 123 for Bar.
• If the user provides Bar 456 tell the user Bar already has a phone number.
• To update a phone-number the user must provide --update Bar 456
• To remove a name the user must provide --delete Bar
• To list all the names the user can provide --list